1. Field of the Invention
This invention relates generally to a mensuration device and method and, more specifically, to a uniquely compact and useful instrument, tool or device for broad use in navigation particularly nautical or aeronautical navigation, in order to determine quickly and accurately the heading direction and distance to be traveled between selected points located on a navigation chart. The device of the invention consists, preferably, of a transparent or semi-transparent base or body, referred to in the specification as a substrate, having preferred compact dimensions of about 5.times.14 inches, for placement over or upon a selected navigation chart to determine heading direction and travel distance. Imprinted, inscribed or otherwise produced on a flat, major surface of the substrate are a circular compass rose, with degree marks for each of its 360.degree., and a novel arrangement of "folded" distance scales which cooperate, in accordance with the practice of the invention, with a cord attached at the center of the compass rose to provide quickly and accurately the desired navigational direction and distance data or information.
2. Description of the Prior Art
In navigation and, in particular, in nautical and aeronautical navigation, it is conventional to use navigation charts in combination with one or more of a variety of hand-held navigational plotting devices, instruments or tools to plot and determine course direction and distance. The available navigation charts come in a variety of formats and, in particular, are scaled in accordance with a number of different distance scales, such as, 1 to 20,000, 1 to 40,000, 1 to 80,000, 1 to 120,000, 1 to 500,000, 1 to 1,000,000, etc. nautical or aeronautical miles. The instruments or devices available for use with such charts to determine navigational headings and/or distances and other navigational information vary dramatically in their accuracy, their reliability and the relative ease or difficulty of their use.
Specifically, it is known in accordance with U.S. Pat. No. 1,638,914 to make available for placement on a chart or map an instrument for providing general compass directions and a direct reading of distances on a tape measure. The instrument disclosed is comprised of a base carrying a circular array of compass point directions, e.g., N, NNE, NE, ENE, E, etc., about its center and having a flat tape, imprinted on one or both sides with selected distance scales. The distance scale tape is disclosed to be operatively associated with the center of the array of compass points, in a variety of ways, to permit simultaneously measuring map or chart distances directly on the tape while, at the same time, providing a general directional reading. The basic instrument disclosed, however, is not designed to facilitate accurate directional or compass orientation of the instrument with a map or chart, or to provide precise readings of heading directions, such as might be provided by conventional string protractors. Also, its distance measuring tapes and various forms of tape holders are subject to abuse and ready damage, rendering the instrument potentially unusable. In addition, the instrument is not designed to provide a straight-edge for drawing course lines, and requires an additional instrument for that purpose.
In U.S. Pat. No. 3,651,574, there is disclosed an even more complicated and cumbersome variant of the instrument disclosed in the above-mentioned patent. The disclosure of U.S. Pat. No. 3,651,574 adds to the basic concept of said earlier patent by including, as a part of the new instrument, an extendible arm for reference with a map edge to facilitate obtaining heading and distance information on a two-sided map where the point of departure is on one side of the map and the point of destination is on the other side. In other respects, the invention of U.S. Pat. No. 3,651,578 again presents most or more of the same type of deficiencies mentioned in connection with U.S. Pat. No. 1,638,914.
Additional prior art patents that are found to relate to a greater or lesser degree to the subject matter of the invention include U.S. Pat. Nos. 1,888,206; 1,984,390; 3,377,706; 3,514,582; 4,120,091; 4,149,316; 4,190,960; 4,327,497; 4,466,191; 4,499,665; Des. 135,282; Des. 135,722; Des. 148,434; Des. 196,604; Des. 209,775 and Des. 216,279. However, none of the mentioned prior art patents is found to teach, suggest or disclose either the unique structure or the novel method of navigation taught by the disclosure of the present invention. Thus, it remains for this invention to satisfy the need for a compact, sturdy, efficient and reliable navigation device for quickly and accurately determining the heading direction and distance to be traveled between selected points located on a navigation chart and to satisfy the need for such a device that can be used effectively and easily in a confined area with limited work space.